It’s hard to believe that an animal could dwarf the basking shark, but try to imagine an animal whose heart is the size of a car, whose tongue weighs as much as an elephant, and who has blood vessels wide enough that a grown man could swim through. Can you picture it? If so, you’re imagining the mighty blue whale (Balaenoptera musculus), the largest animal that has ever lived on Planet Ocean. (Planet ‘Earth’ for all you land-lubbers; I am a marine biologist after all.)

Like the basking shark, however, we know shockingly little about how many are left, about its migrations, and even about where it goes to breed and birth its calves.

Most populations of the “great whales,” including blue whales, suffered massive declines due to commercial whaling during the first half of the 20th Century. Historically, blue whales in the North Pacific Ocean were frequent visitors to British Colombia, Canada, and the Gulf of Alaska, but by the 1960s, had virtually disappeared. Meanwhile, large concentrations of blue whales off California and Baja California, Mexico, have been documented since the 1970s, but the relationships between these observations – and the whale populations themselves – had been unknown.

In a recent study, researchers from British Colombia, Washington and California reported numerous sightings in the last decade of blue whales in their former northeastern Pacific stomping grounds, suggesting that the elimination of whaling has allowed blue whales to reclaim old territory. Most interestingly, the scientists used photo identification to confirm that the whales venturing north belonged to the California feeding population.

Whale biologists had feared that ‘memory’ of historical feeding areas like B.C. and the Gulf of Alaska might have been lost by area-specific intensive whaling activities, but these new findings show that tragedy might have been averted in this case. However, the true causes of this re-expansion in blue whale ranges are unclear; the study’s co-authors suggest that fluctuations in favorable environmental conditions could be driving the perceived changes in blue whale movements.

Nonetheless, although there is still cause for concern about the future of blue whales in the North Pacific, we can be happy to see that they are finding their way back to places they once called home.

As impressed and intrigued as I am with the things that we scientists have learned, it’s what we don’t know that continues to capture my interest and imagination.

The fact that colossal creatures like the basking shark and the blue whale could be in any way mysterious to curious scientists and awestruck observers speaks to nature’s complexity and to our meager understanding of it. These cases show that if we stay in pursuit of the answers we need to know and to protect nature’s wonders, they will reveal themselves to us in time. What we do with this newfound knowledge is up to us.

Calambokidis et al., Insights into the population structure of blue whales in the Eastern North Pacific from recent sightings and photographic identification. Marine Mammals Science (2009), DOI: 10.1111/j.1748-7692.2009.00298.x